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Code Kumite

A Kata is to a Kumite as Programming is to Pair Programming.

The idea behind a Code Kumite is to combine pair programming and test driven development into pair-tdd. The idea came to me while working with someone and teaching him good tdd practices. I found myself being much more critical of his tests than I was of my own, and cheating the implementation to poke holes in his tests. I believe that pairs often produce better code, but the interplay between him writing tests to break my implementation and me implementing to break tests produced better tests and better code.


This project exists to encourage and support a learning process for developers. I believe that Katas (and now Kumites) offer a lot of value in taking a developer to their next level of proficieny. The project as a whole was started to create a Code Kumite Workshop to teach less experienced developers the ideas of TDD, pair programming, and the value of practicing.


I welcome forks that introduce new katas, or new languages for existing katas. At the time of writing, this project supplies the Bowling Kata in PHP only. I intend to create frameworks for Ruby, Python, and Java as time allows. Please feel free to implement these if I have not already, or just add a new Kata for an existing language. I will also be expanding the project as I can.


For a workshop

You will need:

  • A group of people (even number is better)
  • A moderator
  • The requirements of the Kata/Kumite for the language of your choice (see the readme under 'core/')

Break the group up into pairs. If there is an odd number of people, the moderator can be part of a pair. In each pair, one person will start as the Tester, and the other will start as the Implementor.

As the moderator, during the first run walk amongts the groups and provide feedback.

If people get stuck on the implementation for a long period of time, end the round early, and switch roles. On the second round, do the exercise with the group so they can follow along. Even if groups do not get stuck, I recommend doing this during the second run-through anyways, so they can see the proper way.

On your own

This project is focused on the Kumite form of the Kata. As a Kata, simply take the roll of the Moderator, Tester, and Implementer. As an unsupervised Kumite, the Tester should fill the roll of the Moderator.


Throughout the process. The Tester and Implementer should try to avoid copy/paste is allowed. Cut/paste is fine. Copying is to be avoided, and while feeling the urge to copy shows you will probably need to refactor later (and often that you maybe should have refactored earlier), you should write what you need when you need it until you get to the refactor phase.

Try to minimize talking within the pairs until step 4. But please talk as much is as needed to get over implementation hurdles when someone gets stuck. The idea here is to focus on communicating via code. Tests that can communicate requirements to the Implementor without words are better tests.

Step 1: Test Case

Moderator: Provide the Tester with the next case

Step 2: Red

Tester's Turn: Write a single unit test

  • Focus on FIRST
  • Focus on AAA
  • Make your test as descriptive as possible

Step 3: Green

Implementor's Turn: Make the test pass

  • Write as little code as possible - no more than the test demands
  • Do it as quickly as possible - your top priority is to return the build to green

If the implementation is not obvious:

  • Revert the test (commenting out is fine)
  • Refactor the implementation to pass all previous tests with a focus on enabling the implementation of the next test

Step 4: Refactor

  • Do NOT change the scope of any test or the implementation at this time, though you may change the test in order to make sure it's testing what you wanted
  • At this point, the members of each pair may speak to each other freely
  • Discuss potential refactorings
  • Implement refactorings together, as a team
  • Ensure the build does not go red during this process
    • If it does, and the fix is not obvious, immediately revert the changes
  • When you are done:
    • No implementation or test function should be over 5-10 lines of code when you are done
    • All code should be easily understandable

Step 5: Repeat

Each pair should repeat steps 2-4 until they have fully implemented the requirement provided

  • Existing tests may be altered if they are not useful, or not testing what you wanted
  • New tests may be added

Step 6: Commit

Commit your code

git add -A; git commit -m "..."

At this point the moderator should pause the entire group and host a discussion about anything the pairs would like. Encourage conversation and debate.

Return to Step 1 until all requirements have been met


Reflect on the evolution of the tests and implementation:

  • How did the tests change how you coded?
  • Did you ever write more code than you needed?
  • Did you ever write less code than you needed?

Rotate Testers through other groups, so everyone has a new partner, switch roles, and repeat, so that everyone has a chance to be the Tester and the Implementor